The invention relates to an audio device and an audio device security system for installation in a motor vehicle.
An audio device such as a radio in a motor vehicle is prone to theft, and several ways have therefore been developed to deter thieves. In the "keycode" system, a radio has a secure non-volatile memory which stores a fixed but randomly selected four digit "keycode". If the power from the vehicle battery is interrupted, even momentarily, a circuit in the radio detects this event and the radio will not permit full operation until the correct four digit keycode has been entered on a keypad on the face of the radio. Since the radio cannot readily be stolen without interrupting the power, the keycode system deters theft.
One problem with the keycode system is that the power to the radio may be lost for other reasons, for example if the battery becomes discharged or is changed. If the vehicle owner cannot recall or find a record of the radio keycode number, then the owner has to contact the vehicle manufacturer to find out the code. This is inconvenient for the user and expensive for the motor vehicle manufacturer.